Dim StartString As String
Dim DateValue As String
Dim y As Integer

Dim LastRow2 As Long
With Sheets("DataSheet")
LastRow2 = .Cells(.Rows.Count, "L").End(xlUp).Row 'find the last row on column L
    .Columns(13).Insert Shift:=xlToRight 'add a new column to the right of column L
    For i = 1 To LastRow2 'loop through rows
       If InStr(1, .Cells(i, "L"), ",") Then
            .Cells(i, "M").Value = Split(.Cells(i, "L"), ",")(1) 'split after comma
            StartString = .Cells(i, "L").Value
            DateValue = ""
            For y = 1 To Len(StartString) 'loop to remove unwanted characters
                Select Case Asc(Mid(StartString, y, 1))
                    Case 47 To 57
                        DateValue = DateValue & Mid(StartString, y, 1)
                End Select
            Next y
        .Cells(i, "M").Value = DateValue 'return the date
        .Cells(i, "M").NumberFormat = "dd/mm/yyyy" 'format it correctly
        End If
    Next i
End With